The present invention relates to a method and device for cutting a lap in a comber, and more particularly, to a method and device for cutting a lap when changing laps.
In a comber, when the remaining amount of a used lap, or a primary lap, becomes small, lap splicing is performed to overlap and join an end of the primary lap (primary lap end) with a starting end of a new lap reel. When the lap splicing is performed automatically, the primary lap needs to be cut automatically.
Japanese Laid-Open Patent Publication No. 5-117921 discloses a conventional method for automatically cutting a primary lap. In this method, when the remaining amount of the primary lap wound around a bobbin becomes small when cutting the lap, the bobbin is pressed against two lap rollers by further rollers. In this state, the lap sheet is cut by reversing the rotation of the bobbin, that is, by rotating the bobbin in the direction that winds the lap sheet around the bobbin. More specifically, when the bobbin on the lap roller is almost empty, the operation of the base frame is stopped. A pipe presses the lap sheet that is being fed toward a movable guide plate, which is located at a guide position, to hold the lap sheet with the movable guide plate. Then, an air cylinder of a bobbin pressing mechanism is actuated. When the air cylinder is actuated, pressing levers move the bobbin with the further rollers to a pressing position. When located at the pressing position, the bobbin is pressed toward the lap rollers. A lap motor is driven in this state. This rotates the bobbin in the direction that winds the lap sheet around the bobbin and cuts the lap sheet between the pressing position where the lap sheet is pressed by the pipe and an abutment position where the bobbin abuts the lap rollers.
The bobbin pressing mechanism includes two support plates spaced apart by a distance that is substantially the same as the length of the bobbin. Each support plate extends in the vertical direction and includes two guide pins, namely, an upper guide pin and a lower guide pin. Each support plate supports a corresponding one of the pressing levers that includes two elongated holes. More specifically, the elongated holes are engaged with the guide pins so that the support plates support the pressing levers in a movable manner. The pressing levers each include a distal end, to which a corresponding one of the further rollers is coupled. The axis of each further roller extends in the axial direction of the lap rollers. The air cylinder is fixed below the space between the two support plates. A piston rod of the air cylinder is fixed to the middle of another lever so that the other lever is horizontal. The other lever includes two ends, to which the lower ends of the two pressing levers are respectively coupled. The two pressing levers are each moved to a standby position when the piston rod is moved to a projecting position, and the two pressing levers are each moved to a pressing position when the piston rod is moved to a pulling position. When located at the standby position, the two additional rollers are located beside the bobbin. When located at the pressing position, the two additional rollers engage the lower inner circumferential surface of the bobbin and press the bobbin toward the lap rollers.
The method described in Japanese Laid-Open Patent Publication No. 5-117921 requires the bobbin pressing mechanism and the structure in which the fed lap sheet is pressed by the pipe toward the movable guide plate, which is located at the guide position. Further, the method requires the complicated bobbin pressing mechanism including the further rollers that press the bobbin toward the lap rollers while allowing rotation of the bobbin, the pressing levers that rotationally support the further rollers with bearings, and the air cylinder that moves the pressing levers between the pressing position and the waiting position.
When rotation of the bobbin is reversed by the lap rollers without using the bobbin pressing mechanism (pressure applying device), only the weight of the lap bobbin keeps the bobbin held on the lap rollers. When the weight per unit length of the lap is heavy or the fiber length of the lap is long, the lap has a strong tension. In this case, the weight of the bobbin is not enough to resist slipping of the bobbin. This may hinder cutting of the lap and cause the surface of the remaining lap to be uneven.